Sensor and method for manufacturing the sensor
A 3D-printed sensor with a three-dimensional unit cell structure addresses material limitations and resistance value adjustments, enabling precise force detection across diverse applications.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- MERCARI INC(JP)
- Filing Date
- 2022-04-28
- Publication Date
- 2026-06-29
Smart Images
Figure 0007881110000001 
Figure 0007881110000002 
Figure 0007881110000003
Abstract
Description
Technical Field
[0001] The present invention relates to a sensor and a method for manufacturing the sensor.
Background Art
[0002] Development of sensors that detect the presence or magnitude of an external force from the deformation of a material deformed by an external force has been underway. Such sensors can be applied to various input devices, and for example, they have high affinity for devices that involve operations such as pushing or gripping by a user. As one such sensor, there is known a sensor that imparts conductivity by impregnating a porous structure deformed by an external force with conductive ink and detects the user's operation by measuring the resistance value that changes with the deformation (see, for example, Patent Document 1).
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] Although sensors that are crushed and deformed can detect various operations of a user by devising the implementation on a device, and thus expectations for their application are increasing, there has been a problem that the materials that can be used have been limited so far and the expected functions cannot be obtained. For example, when using commercially available foamed materials or porous materials, it is difficult to adjust the amount of deformation with respect to an external force. Therefore, it has been difficult to appropriately set the change in the resistance value with respect to an external force according to the device incorporating the sensor or the usage mode.
[0005] This invention was made to solve such problems and provides a sensor in which the repulsive force against crushing can be adjusted as an input member, and the change in resistance value to external force can be appropriately set depending on the device into which it is incorporated and the manner of use. [Means for solving the problem]
[0006] A first aspect of the present invention provides a sensor that includes a sensor portion comprising a conductive structure in which a unit cell composed of a plurality of columns and beams is continuous in three dimensions, and an output connector that outputs the resistance value of the sensor portion which changes when at least the conductive structure is crushed by an external force.
[0007] Furthermore, the method for manufacturing the sensor in the second aspect of the present invention includes a step of forming the sensor portion by stacking it using a 3D printer. [Effects of the Invention]
[0008] The present invention provides a sensor in which the repulsive force against crushing can be adjusted as an input member, and in which the change in resistance value to external force can be appropriately set according to the device into which it is incorporated and the manner of use. [Brief explanation of the drawing]
[0009] [Figure 1] This is a perspective view showing the overall configuration of the sensor according to this embodiment. [Figure 2] This figure shows the sensor's behavior when detecting an external force. [Figure 3] This figure shows an example configuration of a sensor system that utilizes detection signals from sensors. [Figure 4] This is a conceptual diagram illustrating the conductive path of the sensor section. [Figure 5] This diagram shows how sensors are manufactured using a 3D printer. [Figure 6] This diagram illustrates a setting method for extending the conductive path of the sensor unit. [Figure 7] This is a diagram illustrating the unit cell. [Figure 8] This figure shows the physical properties resulting from differences in the unit cell. [Figure 9] This is an overall diagram of the sensor related to the first application example. [Figure 10] This is an overall diagram of the sensor related to the second application example. [Figure 11] This is an overall diagram of the sensor related to the third application example. [Modes for carrying out the invention]
[0010] Embodiments of the present invention will be described with reference to the attached drawings. In each drawing, components with the same reference numerals have the same or similar configuration. Furthermore, in each drawing, if there are multiple structures with the same or similar configuration, reference numerals may be assigned to some of them, while the same reference numerals may be omitted to avoid complexity. In addition, not all of the configurations described in the embodiments are necessarily essential as means to solve the problem.
[0011] Figure 1 is a perspective view showing the overall configuration of the sensor 100 according to this embodiment. The sensor 100 is a sensor that uses a soft material as the detection member, also known as a soft sensor. In this embodiment, a cubic sensor with sides of approximately 30 mm when not subjected to external force will be described as an example.
[0012] The sensor 100 mainly consists of a sensor unit 110 and two output connectors 120. The sensor unit 110, as will be described in more detail later, is a three-dimensional continuous structure of unit cells 111, which include multiple columns and beams. It has elasticity, deforming according to the magnitude of the external force applied while the external force is present, and immediately returning to its original shape when the external force is removed. The output connectors 120 are connectors for outputting a detection signal indicating the resistance value of the sensor unit 110 to a detection circuit, and are fixed to the sensor unit 110 by being press-fitted into the gaps between the unit cells 111.
[0013] The cable 200 is a cable that transmits the detection signal output from the output connector 120 to the detection circuit, and the connector pin 210 provided at the end is inserted into and removed from the output connector 120.
[0014] As shown in the figure, the x-axis, y-axis, and z-axis are defined. That is, the direction in which the output connector 120 receives the connector pin 210 is the x-axis direction, the direction in which the two output connectors 120 are arranged side by side is the y-axis direction. Also, the direction orthogonal to the x-axis and y-axis is the z-axis direction. In some subsequent drawings, similar coordinate axes are also noted based on the state installed as in FIG. 1, thereby indicating the orientation of the structure represented by each drawing.
[0015] FIG. 2 is a diagram showing the state of the sensor 100 when an external force is detected. In the present embodiment, a usage mode in which the user crushes the sensor 100 with a fingertip is assumed.
[0016] As shown by the white arrow, when the user presses the upper surface (xy plane on the +z-axis side) of the sensor 100 downward (in the -z-axis direction), each unit cell 111 connected to each other is compressed in the z-axis direction, and the sensor unit 110 as a whole is also shrunk and crushed in the z-axis direction. When each unit cell 111 is compressed in the z-axis direction, the contact area between the column beams constituting the unit cell 111 increases and the resistance value between the two output connectors 120 decreases. The resistance value between the two output connectors 120 is detected by the cable 200 connected to each output connector 120 transmitting the detection signal to a detection circuit described later.
[0017] As the amount of crushing of the sensor unit 110 by the user's fingertip increases, the contact area between the column beams constituting the unit cell 111 increases, so the resistance value output from the output connector 120 further decreases. In other words, the sensor 100 can output different resistance values as the contact state between the column beams constituting the unit cell 111 changes in response to crushing by an external force. Note that FIG. 2 shows an example in which the upper surface in the Z-axis direction (the surface on the +Z-axis side) of the sensor 100 is uniformly crushed by a fingertip, but the crushing on this upper surface does not have to be uniform, and at least the contact portion with the fingertip may be shrunk and crushed in the Z-axis direction. That is, the contact portion of the upper surface of the sensor 100 with the fingertip may be crushed more downward (in the -Z-axis direction) in the Z-axis direction than the other portions of this upper surface.
[0018] FIG. 3 is a diagram showing a configuration example of a sensor system that uses the detection signal from the sensor 100. A cable 200 having one end connected to the sensor 100 is connected to a detection circuit 220 at the other end. The detection circuit 220 includes a resistance value detection circuit and detects the resistance value of the sensor 100 from the detection signal received via the cable 200.
[0019] The detected resistance value is A / D converted and delivered to the control device 230 as a digital signal. The control device 230 is, for example, a personal computer (PC) and can perform software control or the like according to the detected resistance value. Also, if it is programmed to recognize that it is OFF if the detected resistance value is greater than or equal to a preset threshold value and ON if it is less than the threshold value, the sensor 100 can also be used as an ON / OFF switch.
[0020] The control device 230 is not limited to a PC; for example, it may be a mobile device such as a smartphone or game console, an electrical appliance such as a vacuum cleaner, a robot, or a mobile device such as an automobile. In other words, the control device 230 can be any device that acquires a digital signal of resistance and controls operations or movements according to this digital signal. Furthermore, the detection circuit 220 may be included in the control device 230, or it may be included in the sensor 100. Alternatively, the sensor 100 and the detection circuit 220 may be integrated into the control device 230.
[0021] Figure 4 is a conceptual diagram illustrating the conductive path of the sensor unit 110. In the example shown in Figures 1 and 2, the sensor 100 according to this embodiment has two output connectors 120 arranged side by side on one side. If the entire sensor unit 110 were a conductive structure, the shortest conductive path would be a straight line connecting the two output connectors 120, so even if the sensor unit 110 is compressed in the z-axis direction, the change in resistance would be minimal. For a sensor, a larger change in output in response to a change in input is preferable as it facilitates signal processing. Therefore, it is preferable to arrange one output connector 120 and the other output connector 120 near opposite diagonal vertices of a cube shape. However, if the output connectors 120 are arranged in this way, the cables 200 connected to them will be drawn out in radiating directions opposite to each other relative to the sensor unit 110, which not only impairs the user's feel but also makes the cable 200 difficult to manage. Therefore, it is desirable that the two output connectors 120 be arranged on the same side at a close distance from each other.
[0022] Therefore, in order to secure a conductive path of a certain length while arranging two output connectors 120 in close proximity, the sensor 100 according to this embodiment is constructed of a conductive structure 112 and a non-conductive structure 113. The conductive structure 112 is a structure in which unit cells 111 are continuous in three dimensions and is conductive. The unit cells 111 of the conductive structure 112 are formed using a flexible filament made of thermoplastic polyurethane (TPU) with a conductive filler added as the material.
[0023] The non-conductive structure 113 is also a structure in which the unit cell 111 is continuous in three dimensions, but it has insulating properties. The unit cell 111 of the non-conductive structure 113 is formed using a flexible filament made of TPU without conductive fillers, for example. Since the sensor part 110 is formed by integrating the conductive structure 112 and the non-conductive structure 113 adjacent to each other, TPU, which has excellent elasticity and toughness, is preferred as a material for the sensor part 110 that is subjected to repeated crushing.
[0024] More specifically, as shown in Figure 4, the sensor unit 110 is interposed such that the non-conductive structure 113 is inserted into a slit-shaped space provided between the two output connectors 120 of the conductive structure 112, from the lower end surface side (the side of the xy plane on the negative z-axis side). In Figure 4, the overall shapes of the conductive structure 112 and the non-conductive structure 113 are represented by straight lines, and the unit cell 111 is not drawn.
[0025] As the non-conductive structure 113 is interposed in this way, the straight line connecting the two output connectors 120 cannot be a conductive path, and as shown by the thick line, the path that bypasses the non-conductive structure 113 becomes the conductive path. Since such a conductive path passes through more unit cells 111, the difference in resistance value between when the sensor part 110 is crushed and when it is not becomes larger, making it easier to detect the change in resistance value in response to the amount of crushing. Therefore, even if it is crushed only slightly, the pressure can be detected more accurately. In particular, the conductive path in Figure 4 has a long distance in the z-axis direction, so it is preferable for usage modes in which the user crushes the sensor part 110 in the z-axis direction, as shown in Figure 2.
[0026] The sensor unit 110 may be formed by separately creating a conductive structure 112 and a non-conductive structure 113, and then inserting and fixing the non-conductive structure 113 into a slit in the conductive structure 112 as shown in Figure 4. However, in this embodiment, it is formed integrally using a 3D printer. Figure 5 shows the process of manufacturing the sensor 100 with a 3D printer 400. Specifically, it shows the process of layering and forming the sensor unit 110 using the 3D printer 400. Note that the method of manufacturing the sensor 100 with the 3D printer 300 is not limited to layering; any method such as stereolithography may be selected.
[0027] The 3D printer 400 includes a stage 410 and a head 420, and a control unit (not shown) controls the head 420 to form a sensor unit 110 on the stage 410. The head 420 is movable in the xy direction (planar direction) and the z direction (height direction) relative to the stage 410, as indicated by the white arrows.
[0028] The head 420 includes a conductive material nozzle 421 and a non-conductive material nozzle 422, both oriented toward the stage 410. The conductive material nozzle 421 is for heating, melting, and extruding conductive flexible filament 423 supplied to the head 420. The non-conductive material nozzle 422 is for heating, melting, and extruding non-conductive flexible filament 424 supplied to the head 420. The extrusion position and amount of the conductive material extruded from the conductive material nozzle 421 and the non-conductive material extruded from the non-conductive material nozzle 422 are controlled by the control unit.
[0029] The 3D printer 400 extrudes conductive and non-conductive materials from the surface of the stage 410 upward (positive z-axis direction) to a predetermined height, solidifies them, and repeats this process to build up the sensor part 110. More specifically, according to the CAD data, conductive material is extruded from the conductive material nozzle 421 at the position where the unit cell 111 constituting the conductive structure 112 is to be formed, and non-conductive material is extruded from the non-conductive material nozzle 422 at the position where the unit cell 111 constituting the non-conductive structure 113 is to be formed.
[0030] In this embodiment, as described above, a TPU containing a conductive filler is used as the conductive flexible filament 423, and a TPU without a conductive filler is used as the non-conductive flexible filament 424. However, the material of the flexible filament is not limited to these. Any material that has excellent elasticity and toughness and can form a unit cell 111 can be used. For example, one of the conductive structure 112 and the non-conductive structure 113 may be made of a polyurethane-based material, and the other of the two may be made of a polyester-based material.
[0031] Next, the method for setting the conductive path will be explained. Figure 6 shows a sensor 100' different from the sensor 100 described above, and illustrates the method for setting the conductive path to extend it. In the figure, the part of the cube shown by the solid line is the conductive structure 112', and the remaining part is the non-conductive structure 113'. The conductive structure 112' has a three-dimensional shape that follows the z-axis positive direction → x-axis negative direction → y-axis positive direction → z-axis negative direction → x-axis positive direction → y-axis negative direction, bordering the cube along the edge line from one end where one output connector 120 is located to the other end where the other output connector 120 is located.
[0032] With a conductive structure 112' having such a three-dimensional shape, conductive paths extending in three axial directions can be set, as shown by the thick lines. By setting such conductive paths, relatively long conductive paths are available in the x, y, and z axes, so not only is crushing in the z axis direction shown in Figure 2 possible, but crushing in the x axis direction and the y axis direction can also be detected with high accuracy. In other words, user movements can be detected regardless of where the sensor 100' is deformed. Therefore, when manufacturing a sensor that is expected to be crushed in three axial directions, it is preferable to set such conductive paths.
[0033] The structure of the sensor unit for setting a longer conductive path is not limited to this. Any structure in which a non-conductive structure is interposed from the end of the conductive structure toward the interior is acceptable, such that the distance of the conductive path between the output connectors 120 is longer than when no intervening structure is present. Even if the conductive and non-conductive structures have complex shapes, they can be manufactured relatively easily by 3D printing, where the sensor unit is integrally layered. For example, even a sensor unit including a spirally shaped conductive structure can be manufactured with a 3D printer.
[0034] Furthermore, in sensors 100 and 100', a structure is adopted in which a non-conductive structure 113 is interposed between the conductive structure 112 and the conductive path in order to extend the conductive path. However, the non-conductive structure can be used for purposes other than extending the conductive path. For example, if it is not desirable to expose the conductive structure to the environment, the entire outer periphery of the conductive structure may be covered with a non-conductive structure.
[0035] Next, we will explain the unit cell. Figure 7 is a diagram illustrating the unit cell. In particular, Figure 7(a) is a perspective view of the unit cell 111 used in the sensor unit 110, and Figure 7(b) is a perspective view of the unit cell 111' in another example.
[0036] The unit cell 111 has a structure in which a skeletal column-beam 111a is inscribed within a cube with sides of 5 mm, with columns and beams extending radially from the center to each vertex, which is a lattice point. The unit cell 111' is also a cube with sides of 5 mm, and in addition to the skeletal column-beam 111a, it includes a frame column-beam 111b that connects the vertices of the upper surface (xy plane on the z-positive side) and another frame column-beam 111b that connects the vertices of the lower surface (xy plane on the z-negative side).
[0037] A unit cell, also called a lattice, is a structure in which multiple columns and beams extend three-dimensionally within a lattice space that forms repeating units such as cubes, and at least a portion of the columns and beams facing each other's boundaries are connected when they are continuous in the three-dimensional direction. Note that the columns and beams may extend diagonally to the unit cell, as shown in the skeletal column and beam 111a, and may extend not only in a straight line but also in a curved shape. Furthermore, the cross-sectional shape of the columns and beams may change along the direction of extension.
[0038] By changing the size of the grid space, the pattern of the columns and beams, or the thickness of the columns and beams, the physical properties of the sensor, such as its elasticity and the amount of change in resistance to compression, can be adjusted. For example, if the columns and beams are made thicker or more numerous, the amount of compression will be reduced even with a large pressing force, and the sensor will feel harder overall. Also, if the pattern of the columns and beams is designed so that adjacent columns and beams come into close contact with even slight deformation, the contact sensitivity of the sensor can be increased.
[0039] Figure 8 shows the physical properties due to differences in the unit cell. Specifically, Figure 8(a) shows the change in load (N) with respect to compression amount (mm), and Figure 8(b) shows the change in resistance value (kΩ) with respect to compression amount. The solid line shows the change in sensor part A consisting of unit cell 111 as shown in Figure 7(a), the dotted line shows the change in sensor part B consisting of unit cell 111' as shown in Figure 7(b), and the dashed line shows the change in sensor part C consisting of a unit cell in which the unit cell 111' as shown in Figure 7(b) has been changed to a size of 6 mm on each side. All are based on measured values. All sensor parts are cube-shaped with sides of 30 mm and have a non-conductive structure as shown in Figure 4. Furthermore, they are compressed downwards (in the negative z-axis direction) as shown in Figure 2.
[0040] As shown in Figure 8(a), in sensor section A, which consists only of skeletal columns and beams in the unit cell, the load changes linearly with respect to the amount of compression, while in sensor sections B and C, which consist of skeletal columns and beams and frame columns and beams, the change is wave-like. On the other hand, as shown in Figure 8(b), the resistance value of all sensor sections gradually decreases with increasing compression. However, in sensor sections B and C, where the degree of occupancy of columns and beams in the grid space is high, the resistance value for the same amount of compression is lower than in sensor section A.
[0041] When forming the sensor part using a 3D printer as in this embodiment, it is easy to adjust the physical properties by, for example, accepting user feedback. For example, user preferences regarding elasticity can be collected via the internet in the form of a questionnaire, and the 3D printer can be configured to automatically select a unit cell with elasticity corresponding to the aggregated results and form the sensor part. Alternatively, the 3D printer can be configured to accept data such as elasticity and resistance change amounts specified by the manufacturer, and automatically select a unit cell suitable for those specifications and form the sensor part. In this case, the 3D printer can store information associating elasticity or resistance change amounts with different unit cells, select a unit cell corresponding to the acquired data such as elasticity or resistance change amounts, and form the sensor part.
[0042] Although the sensor 100 described above had a cubic shape for the sensor part 110, the shape of the sensor part can be varied in various ways depending on the intended use of the sensor, as long as the unit cell is continuously configured in three dimensions. In particular, the surface of the sensor part does not need to be a unit cell boundary, and the unit cell may be divided on the surface. Therefore, it is possible to make part of the sensor part curved or the whole thing spherical.
[0043] Therefore, several application examples of the sensor 100 in this embodiment will be described. In the following diagrams relating to the application examples, the unit cell is omitted to represent the overall shape. Figure 9 is an overall diagram of the sensor 500 relating to the first application example. The sensor 500 has the shape of a duck as a whole and is about the size that fits in the palms of an adult. The sensor 500 can be used, for example, as a toy for children.
[0044] The sensor 500 is almost entirely molded from a conductive structure 512, with a non-conductive structure 513 interposed between them, inserted from below, at a position corresponding to the duck's abdomen. Two output connectors 120 are arranged adjacent to each other on the side of the abdomen, with the non-conductive structure 513 in between. The sensor 500 is connected to a detection circuit and control equipment (not shown) via cables connected to the output connectors 120. For example, when it is crushed in the direction indicated by the white arrow, the control equipment detects the change in resistance and emits a sound that mimics a duck's quack. Furthermore, the volume of the duck's quack can be changed depending on the degree to which the duck-shaped sensor 500 is crushed.
[0045] Figure 10 is an overall view of a stylus pen 690 incorporating the sensor 600 according to the second application example. The stylus pen 690 is a device that is wirelessly connected to, for example, a tablet terminal and transmits the movement of the pen tip in response to user operations to the tablet terminal.
[0046] The sensor 600 has a cylindrical shape overall and is attached to the grip portion of the stylus pen 690. The sensor 600 is almost entirely molded from a conductive structure 612, with a non-conductive structure 613 interposed in a portion of the cylindrical shape corresponding to a certain central angle. The two output connectors 120 are arranged adjacent to each other on the central axis side of the stylus pen 690, with the non-conductive structure 613 in between.
[0047] The stylus pen 690 has an internal detection circuit, and the output connector 120 is connected to a terminal on the detection circuit. The stylus pen 690 also functions as a control device, determining whether a set input has been detected based on the change in resistance value detected by the detection circuit. For example, if the user presses the sensor part in the direction indicated by the white arrow, it is determined that a click operation has occurred.
[0048] Figure 11 is an overall view of the sensor 700 relating to the third application example. In particular, Figure 7(a) is an overall perspective view looking over the top, and Figure 7(b) is an overall perspective view looking over the bottom. The sensor 700 as a whole is cross-shaped, and the four protruding parts function as a cross button, with each being an independent pressing part.
[0049] Sensor 700 is mainly formed by conductive structures 712 on four protruding parts, each of which is divided into a first conductive part 715, a second conductive part 716, a third conductive part 717, and a fourth conductive part 718, which are the targets of crushing. A non-conductive structure 713 is provided in the center of the cross shape to separate each conductive part. Furthermore, within each conductive part, the non-conductive structure 713 is arranged from the bottom to the top so as to divide it in two along the convex direction. On the bottom side of each conductive part, two output connectors 120 are arranged adjacent to each other, with the non-conductive structure 713 arranged along the convex direction in between. In other words, eight cables are connected to sensor 700. Sensor 800 is connected to a detection circuit and control equipment (not shown) via cables connected to the output connectors 120. When each conductive part is crushed in the direction indicated by the white arrow, the control equipment detects the change in resistance value and determines which conductive part has been pressed.
[0050] Although several sensors according to this embodiment have been described above, the sensor can be modified in various ways as long as it includes a sensor part containing a conductive structure in which the unit cell is continuous in three dimensions, and an output connector that outputs a resistance value that changes when the sensor part is compressed. For example, the size and shape of the unit cells that make up the conductive structure and the non-conductive structure may differ from each other. Furthermore, the conductive structure and the non-conductive structure may not only consist of a continuous single unit cell, but may also be composed of a mixture of multiple unit cells. For example, they may be composed of unit cells of the same shape but with different sizes.
[0051] Furthermore, the conductive and non-conductive structures may be colored in different colors. Alternatively, a hard material serving as a base may be embedded in the center of the sensor section. The output connector is not limited to a type of connector that accepts connector pins; any connector capable of outputting a resistance value to the detection circuit is acceptable, such as a simple configuration with wires extending from it. [Explanation of symbols]
[0052] 100, 100', 500, 600, 700…Sensors, 110…Sensor unit, 111, 111'…Unit cell, 111a…Skeleton columns and beams, 111b…Frame columns and beams, 112, 112', 512, 612, 712…Conductive structures, 113, 113', 513, 613, 713…Non-conductive structures, 120…Output connector, 200…Cable, 210…Connector pins, 220…Detection circuit, 230…Control equipment, 400…3D printer, 410…Stage, 420…Head, 421…Conductive nozzle, 422…Non-conductive nozzle, 423…Conductive flexible filament, 424…Non-conductive flexible filament, 690…Stylus pen, 715…First conductive part, 716…Second conductive part, 717…Third conductive part, 718…Fourth conductive part
Claims
1. A sensor unit comprising a conductive structure in which unit cells formed of a conductive material and comprising at least a plurality of columns and beams inside are connected in three dimensions, An output connector that outputs the resistance value of the sensor portion which changes when the conductive structure is crushed by an external force, and A sensor equipped with the following features.
2. The sensor according to claim 1, wherein the conductive structure is formed of an insulating material and is disposed adjacent to a non-conductive structure in which unit cells, each containing at least a plurality of columns and beams, are arranged in a three-dimensionally continuous manner.
3. The sensor according to claim 2, wherein the non-conductive structure is interposed from the end of the conductive structure toward the interior such that the distance of the conductive path between the two output connectors is longer than in the case where the non-conductive structure is not interposed.
4. The sensor according to claim 3, wherein the two output connectors are arranged adjacent to each other on one surface of the conductive structure, with the non-conductive structure in between.
5. The sensor according to claim 1, wherein the unit cell includes a plurality of column beams extending radially from a point within the cell toward the cell endpoint.
6. The sensor according to claim 1, wherein the unit cell includes a plurality of column beams that connect adjacent cell endpoints to form a frame.
7. A manufacturing method for manufacturing the sensor according to any one of claims 1 to 6, comprising the step of stacking and molding the sensor portion using a 3D printer.